We plan to focus on several properties of a form of acetylcholinesterase that is characteristic of this enzyme in neuromuscular junctions and electric organ synapses. Previous reports from our laboratory have described both the isolation of this enzyme from electric organs of the eel Electrophorus electricus and the asymmetric assembly of its catalytic subunits and collagen-like noncatalytic subunits. One objective of the proposal is to develop techniques for investigating the attachment of this enzyme to synaptic membranes and, in particular, to pursue the hypothesis that the collagen-like subunits mediate a localization in the extracellular basement membrane. We plan to prepare antisera to these subunits for eventual use in immunocytochemical studies designed to indicate whether these subunits are unique to acetylcholinesterase or ubiquitous in muscle and/or nerve basement membrane. Preliminary work antigenicity of collagen-like polypeptides, and several approaches are proposed. A second technique to be explored is the radioiodination of both isolated and membrane-bound acetylcholinesterase with exogenous labelling reagents. Enzyme components that are tightly associated with the membrane presumably will be less reactive toward the labelling agents in the membrane-bound state than after solubilization. A second objective is to continue work in our laboratory on the simulation of endplate currents at neuromuscular junctions. We have reported useful initial models for these simulations based on the reaction of acetylcholine with acetylcholine receptor and acetylcholinesterase. We plan a more rigorous computer treatment to generate a single simulated profile that can be compared to experimentally measured endplate currents.